title: Antimicrobial and DNA-binding activities of the peptide fragments of human lactoferrin and histatin 5 against Streptococcus mutans.
abstract: OBJECTIVE
  To investigate the killing effect of two salivary antimicrobial peptides, hLF1-11 and P-113, and identify the antibacterial mechanism of the peptides.
  
  
  METHODS
  The antimicrobial activities of hLF1-11 and P-113 against oral Streptococci strains were determined using the broth microdilution method. The effects of hLF1-11 and P-113 on the bacterial plasma membrane were visualized by scanning electron microscopy. Cell membrane permeability was monitored using the intracellular dye calcein. The subcellular localization of hLF1-11 and P-113 in bacteria was measured by fluorescence light microscopy. An electrophoretic mobility shift assay (EMSA) was performed to evaluate the DNA binding capabilities of hLF1-11, P-113 and MUC7 12-mer.
  
  
  RESULTS
  Both hLF1-11 and P-113 exerted potent bactericidal activities against all selected oral Streptococci. Streptococcus mutans UA 159 was the most susceptible of the oral bacterial species tested to the antimicrobial effects of the three peptides. The cell membranes of bacteria treated with hLF1-11 or P-113 were still intact after 30 min. hLF1-11 and P-113 could penetrate the bacterial cell membranes and accumulate in the cytoplasm in S. mutans. Both hLF1-11 and P-113 showed DNA binding affinity.
  
  
  CONCLUSIONS
  Together, our results demonstrate that hLF1-11 and P-113 display antibacterial activity against dental cavity-inducing S. mutans through an intracellular mechanism that could involve DNA binding. Thus, these peptides might be attractive and valuable candidates for development into effective antimicrobial therapies to combat dental caries.
authors.affiliation: Institute of Stomatological Research, Sun Yat-sen University, 74 Zhong Shang Er Road, Guangzhou 510080, PR China. huolj@mail2.sysu.edu.cn
authors.forename: Lijun
authors.initials: L
authors.lastname: Huo
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Junqi
authors.initials: J
authors.lastname: Ling
authors.forename: Zhixiang
authors.initials: Z
authors.lastname: Peng
authors.forename: Xiangya
authors.initials: X
authors.lastname: Huang
authors.forename: Hongyan
authors.initials: H
authors.lastname: Liu
authors.forename: Lisha
authors.initials: L
authors.lastname: Gu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002463:Cell Membrane Permeability; D015169:Colony Count, Microbial; D003593:Cytoplasm; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D054808:Histatins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007781:Lactoferrin / Q000378:metabolism / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D009077:Mucins / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D012471:Salivary Proteins and Peptides / Q000378:metabolism / Q000494:pharmacology*; D013295:Streptococcus mutans / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D054808:Histatins; C083238:MUC7 protein, human; D009077:Mucins; D010446:Peptide Fragments; D012471:Salivary Proteins and Peptides; C466658:lactoferrin (1-11), human; D007781:Lactoferrin